In a randomized clinical trial of succimer, an oral chelating agent that lowers blood lead concentration, children with blood leads of 20 to 44 micrograms per deciliter were given succimer or placebo when they were about 2 years old and followed with cognitive and behavioral testing. We reported previously that, despite lower blood lead levels during treatment, children given succimer had test scores that were no different from those of children given placebo at ages five or seven years. This year we used the trial data set to determine whether the effects of blood lead on behavior were direct or were mediated through the effect on IQ. We found that lead has direct effects on externalizing behavior (pushing, shouting) but not on internalizing behavior (fears, worries).[unreadable] We have arranged with CDC to analyze blood samples collected in this project for mercury, which will allow a randomized trial of succimer for mercury chelation without enrolling any new subjects or collecting any specimens. We also used trial data to see if chelation therapy lowered blood pressure, which it did not.